1) consular offices start with the assumption that you're going to overstay and can deny you a visa for no particular, objective reason, 2) similarly, immigration officers can deny you entry even if you have a valid visa, 3) you're not technically doing anything illegal by attending Hacker School on a tourist visa (as opposed to, say, working or attending a university).

I'm surprised that applicants volunteer such information. Why not just say you're visiting NYC as a tourist?